June Lockhart as Sheba's mother is a definite not just because it seems obvious, but the "Living Legend" novelization even gave us the detail of Sheba resembling her mother and that was why Cain couldn't open up to her, so it has a "semi-canon" quality of rightness.
As for her name, I came up with "Bethany" in the late 90s when doing my fanfic and I admit at the time I ended up influencing several other authors on that point. However used I am to that name for the character though, I freely admit it's not canon.
As for Ila, in my current fanfic stories (where the character is revealed to be alive and now on board the Pegasus) I am envisioning Lee Remick in the part.